Matrix band retainer



FIG. 1 is a front elevation of a matrix band retainer showing my new design;

FIG. 2 is a rear elevation thereof;

FIG. 3 is a side elevation as seen from the right;

FIG. 4 is an elevation as seen from the side opposite FIG. 3;

FIG. 5 is a top plan view; and

FIG. 6 is a bottom plan view. 

The ornamental design for a matrix band retainer, as shown. 